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Date:   Thu, 24 Dec 2020 17:49:57 -0700
From:   David Ahern <dsahern@...il.com>
To:     YANG LI <abaci-bugfix@...ux.alibaba.com>, ast@...nel.org
Cc:     daniel@...earbox.net, davem@...emloft.net, kuba@...nel.org,
        hawk@...nel.org, john.fastabend@...il.com, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        kpsingh@...nel.org, netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bpf: fix: address of local auto-variable assigned to a
 function parameter.

On 12/24/20 12:01 AM, YANG LI wrote:
> Assigning local variable txq to the outputting parameter xdp->txq is not
> safe, txq will be released after the end of the function call. 
> Then the result of using xdp is unpredictable.

txq can only be accessed in this devmap context. Was it actually hit
during runtime or is this report based on code analysis?


> 
> Fix this error by defining the struct xdp_txq_info in function
> dev_map_run_prog() as a static type.
> 
> Signed-off-by: YANG LI <abaci-bugfix@...ux.alibaba.com>
> Reported-by: Abaci <abaci@...ux.alibaba.com>
> ---
>  kernel/bpf/devmap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index f6e9c68..af6f004 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -454,7 +454,7 @@ static struct xdp_buff *dev_map_run_prog(struct net_device *dev,
>  					 struct xdp_buff *xdp,
>  					 struct bpf_prog *xdp_prog)
>  {
> -	struct xdp_txq_info txq = { .dev = dev };
> +	static struct xdp_txq_info txq = { .dev = dev };
>  	u32 act;
>  
>  	xdp_set_data_meta_invalid(xdp);
> 

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